This application relates to and claims priority, under 35 U.S.C. xc2xa7119, from Japanese Patent Application No. 11-206773 filed on Jul. 21, 1999, the entire contents of which are hereby incorporated by reference herein.
1. Field of the Invention
The present invention generally relates to a device for detecting objects which have been transferred to operate a switch. The device has a contact which comes into contact with a set position (for example, a terminal) of a different kinds of objects, such as a digital video cassette (DVC) and all other types of cassette, a FD and all other types of discs, and so on. The objects have been transferred to operate a switch and thereby, perform different electrical detecting operations. More particularly, the present invention provides a device for detecting objects which have been transferred to operate a switch, wherein the device includes a flexible spring part formed between a mounting plate part and a U-shaped spring part in a contact spring piece, made of a plate spring. The device further includes the mounting plate part, the U-shaped spring part, and a contact part so as to allow for making the spring span longer to equalize, with high precision, the required load for the contact spring piece (i.e., the contact pressure of the contact with the object) and at the same time, to drastically improve the durability of the contact spring piece.
2. Discussion of Background
A device for detecting an object transferred to operate a switch has been conventionally used, wherein a set position of the transferred object, such as a DVC, other types of cassettes, etc., comes into contact with a contact of a contact spring piece to operate the switch, thereby performing different electrical detecting operations. Two kinds of devices have been used for detecting the object transferred to operate the switch, namely, one in which a contact spring piece is made of wire, and another in which a contact spring piece is made of a narrow and long plate spring piece.
The device for detecting an object, which has been transferred to operate a switch and which uses the contact spring piece made of wire as described above, is prepared, for example, as shown in FIG. 9. Referring to FIG. 9, a coil part 108 is shown as being elongatedly attached to the top of an upright mounting part 101. A contact spring piece A1 is elongatedly equipped with an angled contact part 103. The angled contact part 103 is the lower part of the contact spring piece A1. An upright mounting part 101 is inserted into a hole or slit 106 of a back plate 105 of an L-shaped insulating stock 104 and is fixed in the hole of slit 106. A lower end of the upright mounting part 101 extends outwardly past a lower end of a base 107 of the L-shaped insulating stock 104 to form a terminal 101a. A shaft 111 is inserted into the coil part 108. The angled contact part 103 extends outwardly in front of the back plate 105 of the L-shaped insulating stock 104. A lower end of the angled contact part 103 presses against the front end of a slit 110 of the base 107 of the L-shaped insulating stock 104.
Referring to FIG. 9, an object 109 is shown as being moved in a downward direction so as to contact an upper part of the angled contact part 103. Once contact between the object 109 and the angled contact part 103 is established, the object 109 is then continued to be moved downwardly towards a contact or top 103a of the angled contact part 103, while being in contact with the angled contact part 103. The contact between the object 109 and the angled contact part 103 creates a downwardly-directed load L1 and a cross-direction load L2 on the angled contact part 103. The downwardly-directed load L1, which moves the angled contact part 103 downwardly towards the bottom surface of the L-shaped insulating stock 104, is added to the cross-direction load L2, which moves the angled contact part 103 backwardly in the direction of the front surface of the back plate 105. The downwardly-directed load L1 and cross-direction load L2 act as a force for winding a coil of the coil part 108 so that a set position or terminal (not shown) of the object 109 contacts the contact or top 103a of the angled contact part 103. A bending load P5 is applied to the upper part of the contact spring piece A1 to compress and bend the angled contact part 103 of the contact spring piece A1 and the coil part 108 in cross-direction so as to operate the switch in order to perform detection of the object 109.
However, the detecting device of FIG. 9 has disadvantages with respect to the contact spring piece A1 which is made of wire and these disadvantages will be described in more detail, as follows:
(1). Since the coil part 108 is formed by three or four circular windings forming a coil, a certain amount of space is required, i.e., enough space for a shaft 111 of a predetermined diameter and for the width of the three or four circular windings of the coil. Therefore, further miniaturization of the detecting device is made more difficult to accomplish.
(2). Uniform and precise fabrication is not feasible because of the wire making up the contact spring piece A1. In other word, scatter occurs in every contact spring piece A1, particularly, in the spring constant.
(3). Since a shaft 111 should be inserted within the three or four windings of the coil of the coil part 108, the efficiency of the assembly is poor.
(4). Gold-plating of the angled contact part 103 is necessary, but it is not possible to gold-plate only the angled contact part 103 of the contact spring piece A1 because the wire material making up the contact spring piece is long and continuous and therefore, the overall length of the wire must be gold-plated with expensive gold, so that material costs are raised approximately two to three times what they would be if only the angled contact part 103 of the contact spring piece A1 had to be gold-plated.
The disadvantage described in (4) above is the most significant disadvantage.
In spite of having the above-described disadvantages, a contact spring piece A1 made of wire has the advantage of being very durable because the number of windings of the coil of the coil part 108 and the width of the coil can be adjusted.
A contact spring piece A2 can be made of, for example, a long and narrow plate spring. Such a contact spring piece A2 is shown in FIGS. 10 and 11. This type of contact spring piece A2 is coming into wider use as compensating for the disadvantages (1)-(4) of the above-described conventional contact spring piece made of wire.
However, it has become clear that the contact spring piece A2 made of a long and narrow plate spring is fatally poor in durability. A contact spring piece must have sufficient durability when it is subjected to a required load (i.e., contact pressure of the contact with an object). Thus, durability is the most important aspect of a contact spring piece.
This is true because it is the entire upright mounting plate part 101 (i.e., substantially up to a base of the U-shaped spring part 102 as shown in FIG. 10) that is inserted into the hole or slit 106 of the back plate 105 of the L-shaped insulating stock 104 and fixed to be immovable therein, when the contact spring piece A2 is mounted. The contact spring piece A2 includes the U-shaped spring part 102 and the angled contact part 103. The U-shaped spring part 102 is attached to the upper end of the upright mounting plate part 101. The angled contact part 103 is elongatedly attached to the lower part of the U-shaped spring part 102. Referring to FIGS. 11(a) and 11(b), the U-shaped spring part 102 is shown as having a greater width than the contact spring part 103, but a smaller width than the mounting plate part 101.
Referring again to FIG. 10, an obliquely downward load P1 is shown as acting on the upper portion of the angled contact piece 103 and a load P2 is shown as action on a portion of the U-shaped spring part 102. The load P2 compresses and bends the U-shaped spring part 102 in a cross-direction, when an obliquely downward load P1 is applied to the angled contact part 103 of the contact spring piece A2, by a synergistic action of the downwardly-directed load L1 applied to the angled contact part 103 and cross-direction load L2 due to contact of the object 109 with the angled contact part 103 and the further downward movement of the object 109 while being in contact with the contact part 103.
That is to say, the U-shaped spring part 102 is compressed and bent by the load P2 in the cross-direction. Thus, the U-shaped spring part 102 acts in a typical manner in that it is restored to its original state by a release of the load. Additionally, since the conventional contact spring piece A2, shown in FIGS. 10, 11(a) and 11(b), is not provided with the equivalent of the flexible spring part 8 of the present invention as shown in FIGS. 5, 6, 7, and 8(a)-(d), a flexible action does not occur when the object 109 moves downwardly toward the angled contact part 103 so as to frictionally contact the angled contact part 103. Consequently, metal fatigue, caused by frequent application and release of the load P2 on the relatively short span of the U-shaped spring part 102, is entirely concentrated on the U-shaped spring part 102 at a top thereof, so that the U-shaped spring part has the drawback of often breaking in short-term service.
Furthermore, when the required load (i.e., the contact pressure of the angled contact part 103 and the object 109) is adjusted by adjusting the width (thickness) of the plate piece of the U-shaped spring part 102, the load increases sharply by enlarging slightly the width (thickness) because the span between the upper end of the fixed upright mounting plate part 101 and the angled contact part 103 is short. Conversely, the load decreases sharply by diminishing slightly, thereby arising difficulty in adjustment. And, the width (thickness) of the U-shaped spring part 102 with a proper load obtained is extremely poor in durability. Accordingly, solutions to these problems are desirable.
The present invention improves the durability of the contact spring piece and solves the above-mentioned problems of the prior art contact spring pieces by providing a flexible spring part, being made of a plate spring piece and having predetermined dimensions, between the upright mounting plate part of the contact spring piece and the U-shaped spring part of the contact spring piece. The contact spring piece of the present invention, which is made of a plate spring piece, has performance superior to a contact spring piece made of wire, because the span between the upright mounting plate part and the angled contact part is lengthened and because the flexible spring part is provided so as to flex under the load of the contact pressure created when the object contacts the angled contact part.
That is to say, the present invention solves the above-described problems of the prior art by providing a detecting device, which detects when an object is moved downwardly to operate a switch. The detecting device includes a U-shaped spring part which is attached elongatedly to an upper end of an upright mounting plate part. The upright mounting plate part has a lower end which acts as a terminal. An angled contact part has a top or contact and the angled contact part is attached elongatedly to a lower end of the U-shaped spring part. Together the terminal, upright mounting plate part, U-shaped spring part, and angled contact part make up a contact spring piece. However, the different components of the contact spring piece have different widths. More particularly, the upright mounting plate part of the contact spring piece has a predetermined width, wherein the flexible spring piece has a width smaller than the upright mounting plate part, the U-shaped spring part has the same width as the flexible spring part, and the U-shaped spring part has a greater width than the angled contact part. The upright mounting plate part, of the contact spring piece, is inserted into a slit in a back plate of a L-shaped insulating stock and the upright mounting plate part is fixed therein. The upright mounting plate part has a terminal extending from a lower end thereof such that the terminal extends past a base of the L-shaped insulating stock. The angled contact part, attached to the U-shaped spring part, extends outwardly in front of the back plate of the L-shaped insulating stock. A lower end of the angled contact part is inserted into a slit in the base of the L-shaped insulating stock and a front of the angled contact part contacts a front end of the base of the L-shaped insulating stock. The present invention is characterized in that the contact spring piece has a flexible spring part of predetermined dimensions and the flexible spring part is located between the upright mounting plate part and the U-shaped spring part of the contact spring piece. Further, the upright mounting plate part has at least one contact spring piece and the upright mounting plate part is inserted into and fixed in a slit in the back plate of the L-shaped insulating stock such that a terminal extends from of lower part of the upright mounting plate part past a lower end of the base of the L-shaped insulating stock. The upper end of the U-shaped spring part is engaged with a stopping recess located at an upper end of the back plate of the L-shaped insulating stock. The angled contact part is located in front of the back plate of the L-shaped insulating stock, such that a lower end of the angled contact part is inserted into the slit in the base of the L-shaped insulating stock and is pressed to the front end of the base of the L-shaped insulating stock.